Abstract: To analyze the influence of T-junction structure on flow distribution in superheater with tee-junction(T-junction) headers and subsequently solve the problems of tube burst failure occurring to the superheater, numerical simulations were conducted to a superheater model using Fluent software to study the static pressure distribution and velocity distribution in the superheater, the flow distribution in each branch tube, as well as the fluid velocity and static pressure at each branch inlet. Results show that the fluid near to the tee-structure is low in pressure and high in velocity, while that far away from the region is high in pressure and low in velocity; small vortex only forms in eddy region near T-junction while no vortex in other regions at branch inlet; within the header, the flow in branch tube below the eddy region is relatively low, but that facing the header entrance is the highest; by changing the inlet of the 7th and the 11th tube panel into round shape, the branch flow may be increased significantly.